Conversion of hydrocarbon oils



May 11; 1937. LE ROY STORY 2,079,776

CONVERSION OF HYDROCARBON OILS Original Filed Ap ril 21, 1931 FLASH STILL DEFHLEGMATCW INVENTOR. L Y, G. STORY BY M ATTORNEY Patented May 11, 1937 UNITED STATES Ail.

QFFICE Le Roy G. Story, Bronxville, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Original application April 21, 1931, Serial No.

Divided and this application September 28, 1934;, Serial No. 745,887

Claims.

This invention relates to the conversion of hydrocarbon oils and has to do particularly with a combination of liquid phase and vapor phase cracking which provides certain advantages and presents features of novelty that will be more fully described and claimed hereinafter. This application is a division of my copending application S. N. 531,693, filed April 21, 1931.

An important object of the present invention is to produce from a fresh charging stock, essentially, a residue of coke, a distillate of gasoline having a high antiknock value and fixed gases which may be used as fuel or for other purposes as desired.

The invention contemplates the stripping of fresh charging stock by contact with the vapors from a coking operation, the separation of a clean cracking stock for a pressure cracking system, the separation of selected cuts for vapor 0 phase cracking and the coking of the residue liquids from the stripping and pressure cracking operation by the sensible heat of the vapor phase cracked products. With suitable type of apparatus and novel methods of operation the volatile products may be concentrated at one zone in the system whereby a gasoline of high antiknock Value, consisting of both liquid phase and vapor phase cracked products, may be separated, the heavier components fractionated to produce selected cuts which may be subjected separately to a pressure cracking system and a vapor phase cracking system, while the unvaporized residual oil from the system may be reduced to coke in coking stills.

5 The process of the invention is flexible so that a wide selection of cuts for cracking may be made by segregating various fractions according to the desired volatility or refractoriness and each fraction subjected to the most suitable type of con- 40 version operation. Accordingly, the low boiling products vaporized in the pressure cracking operation may be separately dephlegmated to produce selected cuts for vapor phase and liquid phase cracking; the residual liquid or pressure tar may 45 be flash distilled under reduced pressure to likewise produce selected cuts for the same purpose, if desired; or, the entire vapor fraction from both the pressure stills and the flash still may be concentrated in one large tower, which also receives 50 vapors from the crude stripper, and the resulting mixture of vapors fractionated to separate the desired gasoline, and to produce at the same time a fraction suitable for vapor phase cracking stock and a clean condensate adapted for pressure still 55 cracking.

The invention may be more clearly understood by referring to the accompanying drawing wherein an apparatus is shown for conveniently carrying out the invention and forming one embodiment thereof. 5

In the drawing the reference character I represents a heater for heating oil under pressure; 2 and 3 a pair of stills for separating vapors from residual oil; 4 a dephlegmator for dephlegmating or fractionating vapors from the stills 2, 3; 5 10 a vapor phase cracker for cracking oil in the vapor phase; 6 and l a flash still and dephlegmator for vaporizing residue and fractionating the vapors from the stills, 2, 3; 8 and 8a, coke stills for reducing residual oil to coke by the heat of the 5 cracked products from the vapor phase cracker 5; and 9 a combined stripper and fractionating tower for stripping crude and for fractionating any or all the vapors from the stills 2, 3, flash still 6, vapor phase cracker 5, and coke stills 8 and 8a. 20

The heater I comprises any well known type of furnace having a coil or tubular heater I0, located therein, and connected to an extraneous supply line II and a clean distillate charge line l2. A burner l3 supplies heat to raise the oil passing through the coil Ill to conversion temperatures. A transfer line l4, conducts oil from the heater to either or both of the stills 2 and 3 by means of the branches l5 and I6 respectively. 30

The stills 2 and 3 are shown as vertical chambers having a vapor connecting line 20 and a liquid overflow pipe 2 l. The vertical type of still is shown for illustrative purposes only and other shapes and designs of stills may be employed, if desired, with equal success. The stills are preferably insulated to retain the heat content of the oil and provide reaction time at conversion temperatures. Each still is provided with residue draw-off lines 23 and 24 for withdrawing residual liquid continuously or intermittently. A vapor pipe 25, regulated by a valve 26, conducts vapors from the stills 2 and 3 to a line 21, referred to hereinafter. Vapors from pipe 25 may be passed to line 21, by Way of vapor pipe 25' having regulating valve 26, if desired. A branch line 28, in which is interposed a valve 29, serves to conduct the vapors, if desired, to the dephlegmator 4.

The dephlegmator 4 may conveniently take the form of a bubble tower equipped with trays to contact the vapors and reflux condensate. A cooling coil 30 is provided in the top of the dephlegmator to supply cooling thereto by an extraneous cooling medium. A vapor pipe 3! conducts vapors from the dephlegmator to a condenser coil 32. A condensate line 33 serves to convey the condensate from the condenser to a receiver 34 which is equipped with the usual gas release line 35 and liquid draw-ofi pipe 39.

The dephlegmator is further provided with lines 36' and 31, regulated by valves 38 and 39 respectively, communicating with the bottom thereof to withdraw reflux condensate from the bottom of the tower. A line 49, in which is interposed a valve M, connected to the side of the dephlegmator, serves to withdraw a side out therefrom, if desired. The reflux condensate pipes 39 and 31, as well as the side pipe 49, separately connect to a line 27, referred to heretofore, which communicates at different elevations with the upper fractionating section of the tower 9 by means of branch lines 42 and 43. A line 45, regulated by valve 46, communicating with the line 21, leads to the tubes or coil 4'? located in the vapor phase cracking furnace 5.

The vapor phase cracker 5, shown for purposes of illustration as a diagrammatical section, may be any well known or preferred type of vapor phase cracking apparatus. A conyenient type of furnace for such use may be similar to that disclosed in U. S. Patent No. 1,717,334, June 11, 1929, to Luis de Florez. A pipe 48, controlled by valves 49 and 50, connects the cracking coil 41 to the stripper section of the tower 9. Branch lines 5| and 52 connect the line 49 to the coke stills 8 and 8a. A vapor line 53 serves to conduct vapors from the coking stills 8 and 8a to the bottom of the stripper section of tower 9.

Referring now to the flash still 6, a residue line 55 serves to conduct residuum thereto from the stills 2 and 3. A vapor line 56 conducts vapors from the flash drum 6 to the dephlegmator l. A vapor line 58 connects the dephlegmator i to the line 21 referred to heretofore. A residue draw-01f line 69 serves to withdraw residue from the flash still 6. A branch line 6! serves to conduct the residue, if desired, to a charge line 62 leading to the stripper section of tower 9. A reflux condensate line 63 conducts reflux condensate from the bottom of dephlegmator T to the clean distillate charge line 94. A branch line 65, controlled by valves 66 and 6?, connects the reflux line 63 with the line 21, whereby the condensate may be transferred to the fractionator 9. A branch line 99, controlled by valve 69, connects the line 65 to the line 27 ahead of valves 18 and H in line 2'? so that the condensate, if desired, may be sent to the vapor phase cracker via lines 2i and 45. A condensate line 75 serves to withdraw condensate from the middle of dephlegmator l to the line 65.

Referring to the stripper and fractionator 9, it will be noted that the upper section of the tower constitutes a fractionating tower while the lower section constitutes the stripper. The sec tions are separated by a partition having a vapor riser 8| therein so that vapors from the stripper may pass to the fractionator. While the stripper and fractionator are shown as a single tower with the fractionator superimposed on the stripper, nevertheless the two sections may be made as separate units and the inventioncontemplates such an arrangement.

A charge line 92 leads to the top of the stripper to conduct fresh charge thereto as well as residuum from the line Bl, if desired. A residue draw-off line 83 serves to withdraw unvaporized oil from the bottom of the stripper. A branch line 8 having a pump 84' serves to transfer the residuum from line 83, if desired, to the line 98 to be mixed with the cracked products from the vapor phase cracker 5 and thence to be conducted to the coke stills or to the stripper. A branch line 85, controlled by valve 89, connects the line 6! and 85 whereby the residuum from the flash still 6 may be contacted with the products from the vapor phase cracker.

A clean distillate or reflux condensate line 99, connected to line 2?, serves to withdraw condensate collecting in the bottom of the fractionator 9 or condensate in line 2'! to storage or to conduct the condensates to the charge line 84 whence they are forced by pump 9! to the coil ii A condensate line 93, connected to the side of the fractionator, and having a pump 93' serves to conduct, if desired, a side out from the iractionator to the line 45 leading to the vapor phase cracker 5. A vapor line 95 conducts vapors from the top of the fractionator to the condenser coil 96. A condensate line 9'! connects the condenser coil 99 to a receiver 98 which is equipped with the usual gas release line 99 and liquid draw-ofi line 498.

In practicing teh invention with an apparatus such as that shown in the drawing, charging stock, such as crude oil, is charged to the stripper through line 62 wherein the fresh charge comes in contact with the hot vapors therein and the charge may be partially cracked and the lighter constituents vaporized. The vapors, including the volatilized constituents of the fresh charge, pass through the riser ill to the fractionator. A clean distillate collects above the partition 39 and is conducted by the lines 99 and 64 to the pressure cracking coil 9. The clean distillate passing to the coil I9 is prefera ly a cracking stock of the nature of gas oil. If de sired, an extraneous charge of oil may be introduced through the line H. The addition of extraneous oil is sometimes desirable in order to provide a uniform charging rate in case the supply from the fractionator runs low and more particularly is such a supply of charge from line H convenient in starting up operations.

The oil in the heating coil i9 is raised to conversion temperatures of the order of 750 F.-950 F. and a pressure of 200-600 pounds per square inch may be carried on the coil and stills 2 and 3. Two stills are shown in the drawing but any number may be used. Likewise, the stills are shown connected with vapor lines and liquid overflow lines, but it is contemplated that a low liquid level may be maintained in the stills in which case there would be no overflow but instead the hot oil may be charged to one or both stills and the entire contents of the stills maintained substantially as vapors. The vapors from the the stills 2 and 3 pass through the line 25 and may be passed directly to the fractionator 9 through line 27.

In one method of operation the vapors from stills 2 and 3 may be passed through line 28 to the dephlegmator In the dephlegmator the vapors are fractionated to separate a gasoline fraction which is condensed in condenser 32 while the heavier constituents are collected as reflux condensate. The reflux condensate may be collected entirely in the bottom of the tower 4 or separated into selected cuts and one cut taken off as a side stream through line 40. In case a side stream is taken ofi it is preferable to charge this cut to the vapor phase cracker through line 45 While the heavier cut in the bottom of the tower 4 fractionator 9.

is passed through line 36 and line 21 to the fractionator 9 or directly to line 90 to be backtrapped to the heater coil It. When no side out is taken from the tower 4 then the reflux may be passed entirely or in part through lines 31 and 45 to either the vapor phase cracker 5 or the tower 9.

The residue from stills 2 and 3 may be conducted continuously or intermittently to the flash still 5. A reduced superatmospheric pressure is maintained in the still 6 so that the lighter fractions of the residual oil are immediately flashed by their sensible heat into vapors. The vapors pass to dephlegmator I while residue is withdrawn through line to be disposed of as described hereinafter. The vapors in dephlegmator I may be separated into one or more cuts, as desired. In some cases it may be desirable to pass a substantial amount of the vapors to vapor phase cracker 5 and this may be done by suitable regulation of valves "it and H in line 2?, or the vapors by other regulation of the same valves may be sent directly to the fractionator 9. Likewise, one or two cuts of condensate may be made in the tower 1, these cuts being drawn off through lines 53 and 15. In this way a side out may be taken on through line 15 and sent to the vapor phase cracker by suitable regulation of valve 69 in branch line 68 and valve 6'! in line 66, while a heavier condensate from the bottom of tower I may be returned to coil I0 through line 64. In some cases it may be desirable to make a single cut of condensate in tower! and this cut may be withdrawn through line 53 and passed to the coil it or conducted through line to either the vapor phase cracking coil or to the fractionator 9 by suitable regulation of valves 69 and 51 in lines 68 and 56 respectively.

While I have described the manner in which particular fractions from either the dephlegmator t or dephlegmator i may be passed to the vapor phase cracker 5 or the fractionator 9, it is to be understood that selected fractions of liquids and/or vapors from both dephlegmators may be passed simultaneously to the vapor cracker 5 or It will be observed therefore that flexibility of operation is an essential feature of my invention whereby selected cuts may be treated in a manner to provide optimum conditions for both yield and quality of the desired finished products.

The oil in passing through vapor phase cracker 5 is raised to a temperature'suitable for conversion in the vapor phase, say between 950 F. and 1150 F. The hot products of conversion may be transferred through line 48 directly to the stripper section of the tower 9. It is preferable, however, that these products go to the coke stills B and Set by means of lines 5| and 52, in order that the heat thereof may be used for coking the residual oils from the system. Two coke stills are shown, for purposes of illustration, but only one is ordinarily used at a time while the other is cleaned of the coke deposition therein. The vapors from the coke stills pass through lines 53 to the stripper section where they contact the heavy oil charged thereto through line 62.

The residual oil from the system is preferably commingled with the hot vapors from the vapor phase cracking operation. Referring first to the residuum from the flash still, this oil may be passed through lines GI and 62 of the stripper. It is preferable, however, to bypass it through lines 85 and 84 to be commingled with the vapor phase cracked products. Therefore, this residue may be used to cool the cracked products in case they are passed directly to the stripper through line 48 or the mixture of residuum and vapors may be passed through lines 5| and 52 to the coke stills where the residue is reduced to coke by the sensible heat of the vapors. Likewise, the unvaporized oil collecting in the bottom of the stripper is withdrawn through line 83 and passed entirely or in part, alone or in mixture with the residuum from flash still 5, into the line 48 to be treated as just described.

The vapors collecting in the fractionator section of tower 9, which may comprise all or a part of the vapors from the entire system, depending on whether the dephlegmator 4 is by-passed, are

fractionated and the reflux condensate or clean distillate, entirely or in part, passed to the heater coil 10. Sometimes it is desirable to separate the reflux condensate into selected cuts, and therefore, I have shown a line 93 for making a side out to be returned to the vapor phase cracker 5. The latter is particularly advantageous in case the dephlegmator 4 is by-passed and all the vapors concentrated in the fractionator section of tower 9.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

i. The method for conversion of hydrocarbon oils by a series of continuous steps which comprises subjecting hydrocarbon oil to conversion temperatures in a cracking zone, directing resultant cracked products into a separating zone wherein separation of vapors from liquid residue takes place, passing vapors thus separated into a fractionating zone and subjecting the vapors therein to fractionation to form a vapor fraction and a reflux condensate, subjecting said reflux condensate, while retaining heat from its previous treatment and free from added products, to conversion temperatures in the vapor phase in a second cracking zone, flash distilling said liquid residue and commingling resultant residue of the flash distillation with the resultant products of the vapor phase conversion, passing the resultant mixture to a coking zone separate from said separating zone, subjecting the mixture therein to coking, withdrawing vapors from the coking zone and conducting the vapors to a stripping zone, introducing fresh charging stock into said stripping zone, passing unvaporized oil from the stripping zone into the coking zone, passing vapors liberated in the stripping zone to a fractionating zone separate from the first-mentioned fractionating zone and subjecting the vapors therein to fractionation to form a reflux condensate and introducing reflux condensate so formed into one of said cracking zones for conversion.

2. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock comprising residual constituents into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate free from residual constituents of said charging stock, removing said light vapor fraction as a desired product, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors,

in a fractionating zone separate from said stripping zone, to form a light vapor fraction, an intermediate condensate, and a heavy condensate, introducing said heavy condensate into said stripping zone, cracking said intermediate condensate and introducing the resulting cracked products, including vapors formed, into said stripping zone as a source of supply of said highly heated vapors first mentioned, subjecting said liquid residue to a flashing operation with resulting separation into vapors and unvaporized residue, introducing said unvaporized residue into said stripping zone in mixture with the vapor phase cracked products, subjecting the flashed vapors to partial condensation and combining the resulting condensate with the condensate removed from the stripping zone for subsequent cracking.

3. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock comprising residual constituents into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate free from residual constituents of said charging stock, removing said light vapor fraction as a desired product, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, seperating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors, in a fractionating zone separate from said stripping zone, to form a light vapor fraction and a condensate, cracking this condensate and introducing the resulting cracked products, including vapors formed, directly into said stripping zone as a source of supply of said highly heated vapors, subjecting said liquid residue to a flashing operation with resulting separation into vapors and an unvaporized residue, introducing said unvaporized residue into said stripping zone in mixture with the cracked products last mentioned, subjecting the flashedrvapors to partial condensation and combining resulting condensate with the condensate removed from the stripping zone for subsequent cracking.

4. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in con-= tact with highly heated vapors whereby partial vaporization of said stock occurs, directing resultant vapors into a fractionating zone and subjecting the vapors therein to fractionation to form a light vapor fraction and a clean condensate free from residual products, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, directing reslutant products of the conversion into a separating zone wherein separation of vapors from liquid residue takes place, passing vapors thus separated to a fractionating zone separate from both said stripping zone and said fractionating zone thereof, and subjecting the vapors therein to fractionation to form a light vapor fraction and a condensate, removing and condensing said light vapor fraction, subjecting said condensate to vapor phase cracking in a separate cracking zone, introducing resultant cracked products of the vapor phase cracking into a coking zone separate from said separating zone, flash distilling said liquid residue and introducing resultant residue of the flash distillations into said coking zone to effect coking thereof, removing vapors from said coking zone and introducing them into said stripping zone as said highly heated vapors first mentioned.

5. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock comprising residual constituents into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a clean condensate free from residual products, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors, in a fractionating zone separate from said stripping zone, to form a light vapor fraction and a condensate, removing and condensing said light vapor fraction, cracking said condensate last mentioned in the vapor phase and introducing the resulting cracked products into a coking zone in contact with heavy products derived from said liquid residue to produce coking thereof, removing vapors from said coking zone and introducing them into said stripping zone as said highly heated vapors first mentioned, removing unvaporized portions of said fresh charging stock from said stripping zone and introducing the same into said coking zone, subjecting said liquid residue to flash distillation with attendant formation of vapors, fractionating said vapors to produce partial condensation and combining condensate so formed with the condensate withdrawn from said stripping zone for passage through said cracking zone first mentioned.

LE ROY G. STORY. 

